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Solar hot water systems and the SRCC

Solar hot water systems and solar collectors are rated annually by the SRCC (Solar Rating and Certification Corporation). The SRCC uses a Solar Efficiency Factor (SEF) that is comparable to the EF rating system used by EnergyStar. To compare systems, the same equation that is used for EF can also be used for SEF. (Yearly Energy Cost = 365 days X 12.03 kWh/SEF X $/kWh) SRC uses two parameters to calculate the SEF, Qaux and Qpar. Qaux is the daily amount of energy used by the auxiliary water heater or back up element. Qpar is the parasitic energy used by parts of the system such as pumps, controllers, etc. The same hot water load is assumed for all systems, which, depending on size of the system, may skew results.

The SRCC looks at four different types of solar water heating systems: forced circulation, integral collector storage, thermosyphon and self-pumping. The last three types are all passive systems. Additionally, there are three types of fluids that can be used in these systems: potable fluid such as water, a non-toxic heat transfer fluid such as propylene glycol and a toxic heat transfer fluid such as ethanol. The second type of fluid is optimal for our conditions (due to possibilities of freezing).

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